Methods of reverse link power control

ABSTRACT

Methods of reverse link power control are provided. In a first example reverse link power control process, a signal-to-interference+noise (SINR) is measured for a plurality of mobile stations. A power control adjustment is determined for each of the mobile stations based on the measured SINR for the mobile station and a fixed target SINR, the fixed target SINR being used in the determining step for each mobile station and sending the power control adjustments to the mobile stations. In a second example reverse link power control process, one or more signals are transmitted to a base station. A power control adjustment indicator indicating an adjustment to a transmission power level is received. The received power control adjustment is determined based on a measured signal-to-interference+noise ratio (SINR) for the one or more transmitted signals and a fixed target SINR threshold, the fixed target SINR threshold being used for power control adjustment of a plurality of mobile stations.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Example embodiments of the present invention relate generally tocommunications systems, and, more particularly, to wirelesscommunication systems.

2. Description of the Related Art

FIG. 1 illustrates a conventional Code Division Multiple Access (CDMA)100. The CDMA system includes a plurality of user equipments (UEs) 105in communication with one or more serving Node Bs 120/125 over an airinterface. The plurality of Node Bs are connected to a radio networkcontroller (RNC) 130 with a wired interface. Alternatively, while notshown in FIG. 1, the functionality of both the RNC 130 and Node Bs120/125 (alternatively referred to as “base stations”) may be collapsedinto a single entity referred to as a “base station router”. The RNC 130accesses an internet 160 through a gateway support node (GSN) 150 and/oraccesses a public switched telephone network (PSTN) 170 through a mobileswitching center (MSC) 140.

Referring to FIG. 1, in the CDMA system 100, a power control mechanismis typically used to minimize power consumption and interference whilemaintaining a desired level of performance. Conventionally, this powercontrol mechanism is implemented with two power control loops. The firstpower control loop (often referred to as an “inner” power control loop,or “inner loop”) adjusts the transmit power to each mobile station or UE105/110 such that the signal quality of the transmission received at theUE receiver (e.g., as measured by a signal-to-noise ratio) is maintainedat a target signal-to-interference+noise (SINR) ratio, or targetE_(b)/N₀. The target SINR or E_(b)/N₀, where E_(b) is the energy perinformation bit, and N₀ is the power spectral density of theinterference seen by the receiver, is often referred to as a powercontrol set point, or threshold. The second power control loop (oftenreferred to as an “outer” power control loop, or “outer loop”) adjuststhe threshold such that the desired level of performance, e.g., asmeasured by a particular target block error rate (BLER), frame errorrate (FER), or bit error rate (BER) for example, is maintained.

For example, for link (e.g., forward link or reverse link) powercontrol, the inner loop compares a measured SINR or E_(b)/N₀ of thereceived signal to the target SINR or target threshold. The SINR of thereceived signal is periodically measured, for example, at 1.25 msinterval. If the measured SINR or E_(b)/N₀ is smaller than thethreshold, there may be too many decoding errors when the receiver isdecoding frames of a received transmission, such that the FER is outsidean acceptable range (i.e., too high). Accordingly, the receiver requestsan increase in power on the link. If the measured SINR or E_(b)/N₀ islarger than the threshold, the receiver requests a decrease in power onthe link. Here, the decoded transmission may contain little or noerrors, thus the system may be too efficient (FER is far below theacceptable range) and transmit power is being wasted.

The outer loop surrounds the inner loop and operates at a much lowerrate than the inner loop, such as at 20 ms intervals, for example. Theouter loop maintains the quality of service (QoS) of the link. The outerloop establishes and updates the SINR threshold, which is responsive tochanging channel/environmental conditions. The outer loop looks atquality of the link, and if the quality is too poor, the outer loopincreases the threshold accordingly. Alternatively, if the link qualityis too good, (e.g., an FER less than a target FER of about 1% voicetransmissions, higher for data transmissions), the outer loop readjuststhe threshold so as not to unduly waste system resources. In view ofthis, the target SINR is said to be adaptive. And, because this processis performed for each link, each receiver has its own adaptive targetSINR such that the target SINRs of different receivers (e.g., UEreceivers) differ.

FIG. 2 illustrates a conventional inner loop CDMA reverse link powercontrol process. The process of FIG. 2 is described below as performedwith respect to the reverse link from the UE 105 to the Node B 120.However, it is understood that the process of FIG. 2 is representativeof a conventional CDMA reverse link power control between any UE inconnection with any Node B.

Referring to FIG. 2, at the inner loop, the Node B (e.g., Node B 120)measures the SINR for pilot transmissions received from a UE (e.g., UE105) in step S105. The measured SINR measurement (step S105) is either apre- or post-interference cancellation (IC) measurement. In an example,if the measurement of the pilot SINR is performed with post-interferencecancellation, the Node B 120 measures the pilot SINR prior tointerference cancellation, and then measures the residualinterference-to-total interference ratio after the interferencecancellation. The ratio of these two quantities is a measure of thepost-interference cancellation SINR.

The Node B 120 compares the measured pilot SINR with an adaptive targetSINR in step S1 0. The adaptive SINR target is previously set by theouter loop at the RNC 130 so as to satisfy a level of Quality of Service(QoS), reflected by an expected packet error rate (PER) or FER, for eachserved UE (e.g., UE 105, 120, etc.). The adaptive SINR target is not theonly factor affecting the QoS, however, and the adaptive SINR is setwith a consideration of such other factors so as to more accurately tuneto the desired level of QoS. For example, another factor potentiallyaffecting the QoS is a traffic-to-pilot ratio (TPR) at the UE 105. TheTPR at the UE 105 is fixed, and does not “adapt” as described above withrespect to the adaptive target SINR. Here, “fixed” TPR means that, for agiven transfer rate, the TPR is set to a constant value and does notchange.

The Node B 120 sends a transmit power control (TPC) bit to the UE 105 instep S115. A TPC bit is a single bit binary indicator, which is set to afirst logic level (e.g., a higher logic level or “1”) to instruct a UE(e.g., UE 105) to increase transmission power by a fixed amount and asecond logic level (e.g., a lower logic level or “0”) to instruct a UE(e.g., UE 105) to decrease transmission power by the fixed amount. In anexample, if the comparison of step S110 indicates that the measuredpilot SINR is less than the adaptive target SINR, the Node B 120 sends aTPC bit having the first logic level (e.g., a higher logic level or “1”)to the UE 105. Otherwise, the Node B 120 sends a TPC bit having thesecond logic level (e.g., a lower logic level or “0”) to the UE 105.After the Node B 120 sends the TPC bit to the UE 105 in step S115, theprocess returns to step S105.

In a further example, the frequency at which the Node B 120 measures(step S105) the pilot SINR, compares the measured pilot SINR with theadaptive target SINR (step S110) and sends TPC bits (step S115) may bebased on a desired “tightness” of power control as determined by asystem engineer.

While the process of FIG. 2 is being performed at the Node B 120, at theouter loop, the RNC 130 periodically determines whether to adjust theadaptive target SINR based on an analysis of the inner loopcommunications. This determination may be based on a number of criteria.For example, the RNC 130 decreases the adaptive target SINR if the PERor FER is relatively low (e.g., very few non-acknowledgments (NACKs) aresent to the UE 105 indicating failed transmissions) so as to satisfy agiven level of QoS. In another example, the RNC 130 increases theadaptive target SINR if the PER is relatively high (e.g., too many NACKsare being sent to the UE 105) so as to satisfy a given level of QOS. TheRNC 130 then updates the adaptive target SINR used by the Node B 120 inthe process of FIG. 2 in accordance with the determined adjustment.

SUMMARY OF THE INVENTION

An example embodiment of the present invention is directed to a methodof controlling reverse link transmission power in a wirelesscommunications network, including measuring asignal-to-interference+noise (SINR) for a plurality of mobile stations,determining a power control adjustment for each of the mobile stationsbased on the measured SINR for the mobile station and a fixed targetSINR, the fixed target SINR being used in the determining step for eachmobile station and sending the power control adjustments to the mobilestations.

Another example embodiment of the present invention is directed to amethod of controlling reverse link transmission power in a wirelesscommunications network, including transmitting one or more signals to abase station and receiving a power control adjustment indicatorindicating an adjustment to a transmission power level, the receivedpower control adjustment having been determined based on a measuredsignal-to-interference+noise ratio (SINR) for the one or moretransmitted signals and a fixed target SINR threshold, the fixed targetSINR threshold being used for power control adjustment of a plurality ofmobile stations.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given herein below and the accompanying drawingswhich are given by way of illustration only, wherein like referencenumerals designate corresponding parts in the various drawings, andwherein:

FIG. 1 illustrates a conventional Code Division Multiple Access (CDMA)system.

FIG. 2 illustrates a conventional inner loop CDMA reverse link powercontrol process.

FIG. 3 illustrates a CDMA reverse link power control process accordingto an example embodiment of the present invention.

FIG. 4 illustrates a CDMA reverse link power control process accordingto another example embodiment of the present invention.

FIG. 5 illustrates a process of establishing a maximum transmit powerper chip threshold for a mobile station's transmissions according to anexample embodiment of the present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS CDMA Reverse Link PowerControl

A CDMA reverse link power control process according to an exampleembodiment of the present invention will be described below with respectto the conventional CDMA system 100 of FIG. 1. More specifically, theembodiment will be described below as performed with respect to thereverse link from the UE 105 to the Node B 120. However, it isunderstood that the embodiment may also be representative of CDMAreverse link power control between any UE in connection with any Node B.Furthermore, it will be appreciated that the processes of the presentinvention are not limited to the CDMA system of FIG. 1.

In the outer loop, the RNC 130 selects a fixed target SINR or E_(b)/N₀system. As will be described below, the fixed target SINR is fixed forall UEs within the CDMA system 100, and is used in the inner loop forevaluating measured pilot SINRs in order to determine whethertransmission power adjustments should be made. In an example, the fixedtarget SINR may be set in conjunction with an initial traffic-to-pilotratio or TPR to maintain expected CDMA control channel error rates belowan error rate threshold. Error rates (e.g., a frame error rate (FER), apacket error rate (PER), etc.) reflect a Quality of Service (QoS)provided to the UE 105. As discussed in the Background of the Inventionsection, the target SINR and the TPR are two factors which potentiallyaffect the QoS for the UE 105. Here, the RNC 130 sets the fixed targetSINR and the TPRs based on offline link level curves for each served UEconservatively such that the UEs, including the UE 105, are very likelyto attain a threshold QoS level. The setting of “initial” values for thetarget SINR and the TPRs is well known in the art. However, whileconventional inner- and outer-loops and the outer-loop power controlmechanisms adjust the SINR target to satisfy a level of QoS whilemaintaining the TPR at a constant level at given rates for all UEs, aswill be described below, an example embodiment of the present inventionis directed to maintaining the target SINR at a constant level whileadapting the TPR for each served UE.

The inner loop power control performed at, for example, a Node B such asNode B 120, is illustrated in FIG. 3. As shown, the Node B 120 measuresan SINR for a pilot signal received from the UE 105 in step S405. Themeasured SINR measurement (step S405) is either a pre- orpost-interference cancellation (IC) measurement. In an example, if themeasurement of the pilot SINR is performed with post-interferencecancellation, the Node B 120 measures the pilot SINR prior tointerference cancellation, and then measures the residualinterference-to-total interference ratio after the interferencecancellation. The ratio of these two quantities is a measure of thepost-interference cancellation SINR.

The Node B 120 compares the measured pilot SINR with the fixed targetSINR in step S410. The Node B 120 sends a transmit power control (TPC)bit to the UE 105 in step S415. The TPC bit is a single bit binaryindicator which is set to a first logic level (e.g., a higher logiclevel or “1”) to instruct a UE (e.g., UE 105) to increase transmissionpower by a fixed amount and a second logic level (e.g., a lower logiclevel or “0”) to instruct a UE (e.g., UE 105) to decrease transmissionpower by the fixed amount. In an example, if the comparison of step S410indicates that the measured pilot SINR is less than the fixed targetSINR, the Node B 120 sends a TPC bit having the first logic level (e.g.,a higher logic level or “1”) to the UE 105. Otherwise, the Node B 120sends a TPC bit having the second logic level (e.g., a lower logic levelor “0”) to the UE 105. In a further example, the frequency at which theNode B 120 measures (step S405), compares the measured pilot SINR withthe fixed target SINR (step S410) and sends the TPC bit (step S415) maybe based on a desired “tightness” of power control as determined by asystem engineer.

FIG. 4 illustrates a CDMA reverse link power control process accordingto another example embodiment of the present invention. The process ofFIG. 4 illustrates steps performed at, for example the UE 105. In anexample, the UE 105 may be served by the Node B 120 operating inaccordance with the process of FIG. 3.

As shown in FIG. 4, in step S500, the UE 105 establishes communicationwith the Node B 120 using well-known methods. While data is beingtransferred between the UE 105 and the Node B 120, the Node B 120 willperiodically send acknowledgments (ACKs) and non-ACKs (NACKs) to the UE105 to indicate successful or unsuccessful transmissions from the UE105. CDMA transmissions typically include a pilot channel, a pluralityof control channels (e.g., for sending channel quality indicators(CQIs), etc.) and a plurality of traffic channels. The plurality ofcontrol channels and the pilot channel do not typically receive errorfeedback (e.g., ACKs/NACKs). Rather, error feedback is typicallyisolated to the CDMA traffic channels.

Accordingly, since error feedback for the control channels is notprovided under current CDMA protocols, a conservative initialtraffic-to-pilot ratio (TPR) is set in step S505 such that error ratesfor the plurality of control channels are expected to remain below anerror rate threshold. The TPR multiplied by the power level of the pilotsignal of the UE 105 is the power level for transmissions on trafficchannels of the UE 105. As discussed above, the initial TPR may be setin conjunction with the target SINR to conservative levels in order tomaintain the control channel error rates below the error rate threshold.As discussed in the Background of the Invention section, the target SINRand the TPR are two factors which potentially affect the QoS for the UE105. The RNC 130 sets the fixed target SINR and the initial TPRs foreach served UE conservatively such that the UEs, including the UE 105,are very likely to attain a threshold QoS level, as reflected by FER,PER, etc. In an example, the initial TPR may be a system designer's“best guess” for a good starting point for an adaptive TPR. The value ofthe initial TPR is not critical for the operation of the process of FIG.4 because, as will be discussed below, the initial TPR is updated oradjusted to reflect and respond to actual operating conditions.

The UE 105 receives ACKs/NACKs from the Node B 120 in response to datapackets transmitted to the Node B 120 in step S510. Based on thereceived ACKs/NACKs, the UE 105 determines whether the actual, currenterror rate is below the error rate threshold in step S515. As discussedabove, the initial TPR is set (step S505) based on an expected errorrate. Thereafter, the TPR is adjusted by the UE 105 in step S515 basedon actual operating conditions. If the actual operating conditionsindicate that the error rate is above the error rate threshold (e.g.,worse than expected), the TPR is increased (e.g., by a first fixedamount) in step 515. For example, if the UE 105 attempts to transmit agiven data packet n or more times without a receiving an ACK, the TPR isincreased by the first fixed amount. Alternatively, if the actualoperating conditions indicate that the error rate is below the errorrate threshold (e.g., better than expected), the TPR is decreased (e.g.,by a second fixed amount) in step S515. For example, if a given datapacket is transmitted by the UE 105 and acknowledged within n attempts,the TPR is decreased by the second fixed amount. For example, if therequirement is that the error rate after 4 HARQ attempts is x=1%, thenwe set the TPR_downstep/TPR_upstep=x/(1−x) . In this case, whenever apacket succeeds in less than 4 attempts, the TPR is decreased byTPR_downstep, and if it fails after 4 attempts, the TPR is increased byTPR_upstep.

However, it is understood that the transmit power levels set by the TPRmay have both physical constraints and software constraints. A physicalconstraint of the transmit power level set by the TPR is an actualphysical transmission threshold (i.e., a maximum transmission powerlevel for the UE 105 at its highest power settings). A softwareconstraint is an artificial maximum transmit power level (e.g.,hereinafter referred to as a “maximum transmit power per chipthreshold”) typically set by the outer loop so as to reduce overallsystem interference by not allowing all users to transmit at theirhighest possible levels. An example of establishing the maximum transmitpower per chip threshold is described later with respect to FIG. 5.After the TPR is adjusted in step S515, the process returns to step S510and awaits additional ACKs/NACKs from the Node B 120.

In another example embodiment of the present invention, referring toFIG. 4, the continual adjustment of the TPR in step S515 for Hybrid-ARQ(HARQ) channels may allow a target PER or QoS to achieve a giventhreshold after a given number of transmissions based on the ACKs/NACKsreceived in step S510.

In another example embodiment of the present invention, referring toFIG. 4, if the UE 105 is engaged in soft handoff (e.g., with Node Bs 120and 125), the UE 105 receives ACKs/NACKs on multiple legs (e.g., frommultiple Node Bs) and the determination of the actual error rate in stepS515 is thereby based on ACKs/NACKs in a plurality of sectors. In thiscase, the TPR adjustment performed in step S515 is based on theACKs/NACKs received from the Node Bs 120/125 involved in the softhandoff.

Numerous advantages of the “fixed” target SINR as opposed to theconventional adaptive target SINR will be readily apparent to one ofordinary skill in the art. For example, a SINR target update procedure,conventionally performed at the outer loop (e.g., at RNC 130), need notbe performed. Thereby, numerous frames conventionally devoted to theSINR target update procedures may be used for other purposes. Theprocessing conventionally performed by the outer loop or RNC 130 isoffloaded onto the UE 105 in example embodiments of the presentinvention because the UE 105, when engaged in soft handoff, uses theACKs/NACKs from all Node Bs 120/125 in its active set (e.g., a set ofNode Bs with which the UE 105 communicates with during soft handoff) todetermine whether to adjust the TPR, in contrast to the outer loop orRNC 130 determining whether to adjust the target SINR.

While the example CDMA reverse link power control process was describedas implemented within the conventional CDMA system 100 of FIG. 1, theCDMA reverse link power control process may alternatively be applied inany system capable of operating in accordance with CDMA protocols, suchas a hybrid Orthogonal Frequency Division Multiple Access (OFDMA)/CDMAsystem.

In another example, while not described in this application, maintainingthe fixed target SINR may simplify OFDMA reverse link power controlbecause the CDMA measured pilot SINR (e.g., which may be used in anOFDMA reverse link power control process) may be predicted with greateraccuracy at the UE 105.

In another example, the above-described CDMA reverse link power controlprocess may be employed at an interference cancellation receiver becausethe TPRs at the UEs (e.g., UE 105) may be adjusted in step S520 toaccount for interference at a plurality of traffic channels.

Maximum Mobile Station Transmit Power

An example of establishing a maximum power per chip threshold for the UE105's transmissions will now be described. In an example, UEs locatednear edges or boundaries of cells (e.g., between Node B 120 and Node B125) have more affect on neighboring cell's interference as compared toUEs located in close proximity to a serving Node B (e.g., near acentered position of the cell). If no control is maintained on the peakpower with which a given UE may transmit, overall system interferencemay increase. The following example of establishing a peak power perchip or maximum transmit power level for a UE within the conventionalCDMA system 100 is given as a function of the UE's location with respectto a plurality of cells. Further, while the below example embodimentsare described with respect to the UE 105 having the Node B 120 as aserving Node B and the Node B 125 as a neighboring Node B, thisparticular arrangement is given for example purposes only and it will bereadily apparent that the below maximum transmit power per chip controlprocess may alternatively be applied at any UE within the CDMA system100.

Each of the Node Bs (e.g., Node Bs 120, 125, etc.) within the CDMAsystem 100 periodically measures an amount of received outer-cellinterference (e.g., interference from cells other than a Node B's owncell). Each of the Node Bs compares the measured outer-cell interferencewith an outer-cell interference threshold Io_(thresh). In an example,the RNC 130 may set the outer-cell interference threshold Io_(thresh)for the Node Bs 120/125 Each of the k Node Bs transmits (e.g., to allUEs within range, such as the UE 105) an Interference Activity Bit (IAB)based on the comparison. In an example, referring to a Node B “p”, ifthe comparison indicates that the measured outer-cell interference isgreater than the outer-cell interference threshold Io_(thresh), thenIAB(p)=1, wherein Node B p is representative of one of the Node Bswithin the CDMA system 100. Otherwise, if the comparison indicates thatthe measured outer-cell interference is not greater than the outer-cellinterference threshold Io_(thresh), then IAB(p)=0. It is understood thatthe IABs may be transmitted from one or more Node Bs at once such thatmultiple IABs may be received by a UE within the CDMA system 100, inpart based on the UE's position relative to neighboring or serving NodeBs within the CDMA system 100. A maximum transmit power per chipthreshold adjustment process, performed at the UEs within the CDMAsystem 100, taking into account the IABs transmitted by the Node Bs willnow be described below with respect to a representative UE 105 in FIG.5.

FIG. 5 illustrates a process of establishing a maximum transmit powerper chip threshold for a UE's transmissions according to an exampleembodiment of the present invention. The example embodiment of FIG. 5 isdescribed below with respect to a representative UE (e.g., UE 105) and kNode Bs (e.g., Node B 120, 125, etc.) within the conventional CDMAsystem 100, wherein k is an integer greater than or equal to 1. Thesteps illustrated in FIG. 5 and described below are performed at, forexample, the UE 105 of FIG. 1. The representative UE 105 is notnecessarily in active communication with more than one of the k Node Bs(e.g., although it may be, such as in soft handoff mode), but therepresentative UE 105 is capable of “listening” to or receiving signalsfrom all of the k Node Bs. Accordingly, it will be appreciated that thenumber k may vary based on the UE 105's position within the CDMA system100. For example, if the UE 105 is in very close proximity to a servingNode B such as Node B 120, k typically equals 1. As the UE 105 becomescloser to an edge of a cell, k is typically greater than 1.

In the example embodiment of FIG. 5, in step S600, the maximum transmitpower per chip threshold of the UE 105 being served by the Node B 120 isinitialized, by the UE 105, toP _(max)(1)=Io _(thresh)/max(G(d)), d=1, . . . , k  Equation 3wherein Pmax(1) denotes a maximum power for an initial time period,Io_(thresh) denotes an outer-cell interference threshold (e.g., anamount of outer-cell interference that can be tolerated), and G(d)denotes an average channel gain from the UE 105 to a dth Node B amongthe k Node Bs, wherein d is an integer from 1 to k. In an example, theG(d) measurements are based on SINR measurements on the common pilot andpreamble, and the outer-cell interference threshold Io_(thresh) isdetermined by a design engineer.

The UE 105 receives the IABs (discussed above prior to FIG. 5) from eachof the k Node Bs in step 605 and determines whether an adjustment to themaximum transmit power per chip threshold is required in step S610. Ifstep S610 determines that an adjustment is necessary, a power adjustmentis calculated for the UE 305 in step S615. Otherwise, the processreturns to step S605. In step S615, the UE 105 establishes a tokenbucket for the transmission power resource called Pc_(bucket)(t), whichdenotes the instantaneous updated value of the transmit power resourcebased on the received LABs, expressed asPc _(bucket)(t)=Pc _(bucket)(t−1)−ΔP _(down)  Equation 4if any of the IABs received by the UE 105 are set to “1”, whereinΔP_(down)=w*max(G(y)), wherein y denotes y Node Bs among the k Node Bswhich are sending the IAB equal to “1” at time t, and w is a fixedweight factor determined by a design engineer.

Pc_(bucket)(t) is alternatively expressed asPc _(bucket)(t)=Pc _(bucket)(t−1)+ΔP _(up)  Equation 5if all of the IABs received by the UE 105 are set to “0”, wherein “t”denotes a current time period and “t−1” denotes a previous time period,and ΔP_(up) is expressed byΔP _(up) =[x/(1−x)]ΔP _(down)wherein x is equal to the probability that the outer-cell interferencemeasured by a given Node Bis greater than the outer-cell interferencethreshold Io_(thresh). In an example, the probability “x” is based on acoverage requirement for the given Node B (e.g., Node B 120). In afurther example, the probability “x” is determined during deployment orinstallation of the CDMA system 100.

P_(bucket)(t) is an averaged version of Pc_(bucket)(t), and is expressedasP _(bucket)(t)=P _(bucket)(t−1)+Pc _(bucket)(t)−P _(max)(t−1)  Equation6

P_(max)(t) evaluates toP _(max)(t)=min(P _(max)(t−1), P _(bucket)(t))  Equation 7

if a new encoder packet is scheduled for transmission from the UE 105 tothe Node B 120, andP _(max)(t)=P _(bucket)(t)−P _(margin)  Equation 8

if a new encoder packet is not scheduled for transmission, whereinP_(margin) is an offset value which is greater than or equal to 0 toensure the bucket does not become empty during the transmission of theencoder packet. In an example, a data rate for the new encoder packet isselected such that P_(max)(t) is set to a sufficient power level so asto achieve a threshold level of spectral efficiency.

Once the maximum transmit power per chip threshold P_(max)(t) is set inaccordance with one of Equations 7 and 8 in step S615, the processreturns to step S605.

Accordingly, with the above example methodology described with respectto FIG. 5, one of ordinary skill in the art will appreciate that UEscloser to a greater number of Node Bs (e.g., further away from a servingNode B and closer to cell edges) adjust the maximum transmit power perchip threshold with larger steps, whereas UEs closer in proximity to theserving Node B react more slowly to the IAB bits. The combination of thepilot reference power (Po(t)) and the maximum allowed data/pilot powerper chip may be used in the computation of the spectral efficiency asrequested by the UE.

Example embodiments of the present invention being thus described, itwill be obvious that the same may be varied in many ways. For example,while above-described with respect to a conventional CDMA wirelesscommunication system, it will be appreciated that the above-describedCDMA reverse link power control methodology can be alternatively appliedto any wireless communication system operating in accordance with CDMA(e.g., a hybrid OFDMA/CDMA system).

Further, it is understood that a Node B and a UE may alternatively bereferred to as a base station (BS) and a mobile station (MS) or mobileunit (MU), respectively.

Such variations are not to be regarded as a departure from the exampleembodiments of the invention, and all such modifications are intended tobe included within the scope of the invention.

1. A method of controlling reverse link transmission power in a wirelesscommunications network, comprising: measuring asignal-to-interference+noise (SINR) for a plurality of mobile stations;determining a power control adjustment for each of the mobile stationsbased on the measured SINR for the mobile station and a fixed targetSINR, the fixed target SINR being used in the determining step for eachmobile station; and sending the power control adjustments to the mobilestations.
 2. The method of claim 1, wherein each power controladjustment is represented by an associated transmission power control(TPC) bit.
 3. The method of claim 1, further comprising: selecting thefixed target SINR so as to maintain error rates on a communicationchannel in the wireless communications network below an error ratethreshold.
 4. The method of claim 1, wherein the determining stepcompares the measured SINR with the fixed target SINR, wherein each ofthe power control adjustments instructs the mobile station to increase atransmission power level if the measured SINR is less than the fixedtarget SINR and instructs the mobile station to decrease thetransmission power level if the measured SINR is not less than the fixedtarget SINR.
 5. The method of claim 1, further comprising: measuringouter-cell interference; and transmitting a first interferenceindicating signal indicating whether the measured outer-cellinterference exceeds an outer-cell interference threshold.
 6. The methodof claim 1, wherein the wireless communications system is a CodeDivision Multiple Access (CDMA) system.
 7. The method of claim 1,wherein the wireless communication system is a hybrid OrthogonalFrequency Division Multiple Access (OFDMA)/Code Division Multiple Access(CDMA) system.
 8. A method of controlling reverse link transmissionpower in a wireless communications network, comprising: transmitting oneor more signals to a base station; and receiving a power controladjustment indicator indicating an adjustment to a transmission powerlevel, the received power control adjustment having been determinedbased on a measured signal-to-interference+noise ratio (SINR) for theone or more transmitted signals and a fixed target SINR threshold, thefixed target SINR threshold being used for power control adjustment of aplurality of mobile stations.
 9. The method of claim 8, furthercomprising: adjusting the transmission power level in accordance withthe received power control adjustment indicator.
 10. The method of claim8, further comprising: receiving a plurality of interference indicatingsignals from different base stations; and determining whether to adjusta maximum transmit power threshold based on the plurality ofinterference indicating signals, the maximum transmit power thresholdindicating a maximum permitted transmission power level below whichtransmissions are constrained.
 11. The method of claim 10, furthercomprising: increasing the maximum transmit power threshold if at leastone of the plurality of interference indicating signals indicates anouter-cell interference exceeding an outer-cell interference threshold.12. The method of claim 11, wherein the increasing step increases themaximum transmit power threshold by a fixed amount.
 13. The method ofclaim 11, wherein the fixed amount is expressed byP _(up) =[x/(1−x)]*P _(down) wherein P_(up) is the fixed amount, x is aprobability that the measured outer-cell interference will exceed theouter-cell interference threshold, and P_(down) is a downward fixedamount for decreasing the maximum transmit power threshold.
 14. Themethod of claim 10, further comprising: decreasing the maximum transmitpower threshold if the plurality of interference indicating signals donot include at least one interference indicating signal indicating anouter-cell interference exceeding the outer-cell interference threshold.15. The method of claim 14, wherein the decreasing step decreases themaximum transmit power threshold by a fixed amount.
 16. The method ofclaim 15, wherein the fixed amount is represented byP _(down) =W*(max(G(d)) wherein P_(down) is the fixed amount, max(G(d))denotes a maximum average channel gain from among average channel gainsfor d base stations, the d base stations transmitting d interferenceindicating signals indicating an outer-cell interference exceeding theouter-cell interference threshold.